cp's OEIS Frontend

A274094 a(0)=0; thereafter (-1)^(n+1)*n appears n times.

%I A274094 #30 Nov 28 2024 17:26:54
%S A274094 0,1,-2,-2,3,3,3,-4,-4,-4,-4,5,5,5,5,5,-6,-6,-6,-6,-6,-6,7,7,7,7,7,7,
%T A274094 7,-8,-8,-8,-8,-8,-8,-8,-8,9,9,9,9,9,9,9,9,9,-10,-10,-10,-10,-10,-10,
%U A274094 -10,-10,-10,-10,11,11,11,11,11,11,11,11,11,11,11,-12,-12,-12,-12,-12,-12,-12,-12,-12,-12
%N A274094 a(0)=0; thereafter (-1)^(n+1)*n appears n times.
%H A274094 Chai Wah Wu, <a href="/A274094/b274094.txt">Table of n, a(n) for n = 0..10011</a>
%p A274094 s1:=[0];
%p A274094 for n from 1 to 15 do
%p A274094 for i from 1 to n do
%p A274094 s1:=[op(s1),(-1)^(n+1)*n]; od: od:
%p A274094 s1;
%t A274094 Join[{0}, Flatten[Table[(-1)^(n+1)*n, {n, 15}, {n}]]] (* _Paolo Xausa_, Sep 30 2024 *)
%t A274094 Join[{0},Flatten[Table[PadRight[{},n,(-1)^(n+1) n],{n,15}]]] (* _Harvey P. Dale_, Nov 28 2024 *)
%o A274094 (Python)
%o A274094 A274094_list = [0]+ [i for n in range(1,142) for i in [n if n % 2 else -n]*n] # _Chai Wah Wu_, Jun 11 2016
%o A274094 (Python)
%o A274094 from math import isqrt
%o A274094 def A274094(n): return m if (m:=isqrt(n<<3)+1>>1)&1 else -m # _Chai Wah Wu_, Nov 05 2024
%Y A274094 Cf. A002024, A274093.
%Y A274094 Partial sums of A010816.
%K A274094 sign
%O A274094 0,3
%A A274094 _N. J. A. Sloane_, Jun 10 2016